The invention relates to a vehicle having an air-guiding device arranged in front of a vehicle wheel on a lower side of the vehicle.
From European Patent document EP 1 674 381 B1, an air-guiding device for a vehicle is known, which is arranged in the region in front of a vehicle wheel and projects downward in the direction of the road. The air-guiding device has an air-guiding body, which is convexly curved on its front side facing away from the wheel, and which, on at least one segment of its free end section, has a separation edge in order to reduce a flow pressure acting upon the wheel and reduce a total air drag of the vehicle. The method of operation on which the air-guiding device is based represents a so-called flow partition of the rotating wheel as well as of the respectively assigned axle geometry. Downstream of the air-guiding device, a wake space is generated in the flow, which partitions off components potentially exposed to the flow, such as a vehicle wheel and an axle geometry, in order to reduce the total air drag of the vehicle.
As a result of the occurring turbulent flow and the accompanying flow separation, however, another air drag is generated in the region of the vehicle which is related to the extent of the wake space. In particular, the resulting typical diagonal flow against the wheels contributes to the total air drag. Furthermore, an aerodynamically unfavorable situation is generated as a result of the turbulent flow against the vehicle underbody situated downstream of the air-guiding device.
It is an object of the invention to provide a vehicle having a low total air drag.
This and other objects are achieved by a vehicle according to the invention designed with a three-dimensionally shaped air-guiding device, which is constructed with an aerodynamically effective surface or guiding surface. The surface essentially extends in the vertical direction of the vehicle and is formed by a side region facing the vehicle center.
The air-guiding device is arranged in front of a vehicle wheel on a lower side of the vehicle and includes an air-guiding body, which has the guiding surface extending essentially in the vertical direction of the vehicle and facing a vehicle center. The body includes a bottom region which faces an underlying surface and is connected to the guiding surface and is spaced away from the lower side.
In order to be able to orient an air stream or flow on the outer side of the air-guiding body to a desired extent, an outer region of the air-guiding body, which faces away from the vehicle center and is connected with the bottom region, is constructed with a convex curvature with respect to an outer side of the vehicle. The air stream can be directed by way of the outer region of the air-guiding body in the direction of an outer flank of the vehicle wheel in order to minimize or avoid the transverse flow against the vehicle wheel.
Furthermore, an air stream can be oriented by way of the guiding surface in the longitudinal direction of the vehicle, whereby turbulences are reduced during the flow separation in the region of blunt wheel baffle bodies as well as a diagonal flow against the vehicle wheels or the front wheels of a vehicle, particularly in the region of the rim base.
By way of the invention, it is achieved that the air stream which, in the region of the vehicle wheels, particularly in the region of the front wheels, in principle, flows in with a flow direction pointing diagonally to the outer side of the vehicle, is oriented by the guiding surface in the longitudinal direction of the vehicle. This reduces the above-mentioned diagonal flow, particularly against the front wheels, in which case, because of the pressure conditions in the region of the vehicle wheel, the air stream is nevertheless deflected slightly in the direction of the wheel interior and is guided at least partially into the wheel interior, whereby the cooling of the wheel brake is promoted.
In this context, the term “wheel baffle bodies” subsumes aerodynamic components which are arranged in front of a vehicle wheel and are also provided for shielding a lower side of the wheel house and constructed within the scope according to the invention.
In a further development of the invention, the air stream can be oriented by way of the guiding surface additionally in the direction of the vehicle center. In this case, by way of a corresponding design of the guiding surface, a portion of the air stream is oriented in the direction of the vehicle center and is thereby steered away from the interior side of the wheel, so that the flowing-in of flowing air into the rim base is reduced. A lowering of the air drag coefficient is connected with the above. However, simultaneously, as a result of the reduced flowing of air stream into the rim base, the cooling of the wheel brake is reduced, so that this measure has to be adapted to the overall concept of the vehicle. This measure can, for example, be used in the case of vehicles where the focus is on the reduction of fuel consumption.
By way of the guiding surface or the side region and an edge provided in the joint or transition region between the guiding surface and the bottom region, which edge is constructed to essentially extend in the longitudinal direction of the vehicle, the flow is captured in a region of the air-guiding body facing the front side of the vehicle in the flow direction and is oriented by way of the side region or the guiding surface at the air-guiding body or along the wheel baffle body in the longitudinal direction of the vehicle and even in the direction of the vehicle center.
When the guiding surface is arranged to extend at least approximately at a right angle with respect to the lower side of the vehicle, the tendency of the flow to flow over the air guiding body, starting from the vehicle center in the direction of the outer side of the vehicle essentially in the transverse direction of the vehicle will be minimized, whereby the flow guidance can be oriented along the interior region of the air-guiding body to the desired extent in the longitudinal direction of the vehicle or also in the direction of the vehicle center.
When the air-guiding body projects beyond the vehicle underbody in the flow direction increasingly in the direction of the underlying surface of the vehicle, the flow in the region of the air-guiding body is guided with low losses away in the downward direction by the wheel house following the air-guiding body in the flow direction with respect to the vertical direction of the vehicle.
When the guiding surface of the air-guiding body and the edge of the joint region are constructed with a concave curvature with respect to the vehicle center, the flow will at first attach itself in the forward region of the air-guiding body without deflections that increase the air drag. Subsequently, the flow is guided away from the side region, corresponding to the curvature radius of the side region, from the vehicle wheel following the air-guiding body, the assigned axle geometry as well as the wheel house in the longitudinal direction of the vehicle and, in the case of a corresponding length of the air-guiding body, under certain circumstances, additionally deflected in the direction of the vehicle center.
For this purpose, it is particularly advantageous for a space between the guiding surface or side region and the vehicle center to increase starting from the forward region of the side region in the direction of the rearward region of the guiding surface and, under certain circumstances, to even decrease again in the direction of the vehicle center. This is a result of the fact that the flow takes place onto the lower side of a vehicle starting from its forward center stagnation point at a vehicle-specific flow angle with respect to a longitudinal axis of the vehicle in the direction of the exterior sides of the vehicle, and the diagonal flow in the region of the lower side of the vehicle is then guided with low losses to the desired extent away from the vehicle wheel, the respectively assigned axle geometry and the wheel house from the air guiding body or is guided past it with low losses.
In addition, the air-guiding device may be constructed with an additional air-guiding body or with a wedge or a similar geometry, which is arranged between the air-guiding body and the vehicle center. The flow is then easily and at low losses deflected at the lower side of the vehicle, and the flow is primarily guided by way of the chassis and the rear edge of the wheel house.
The additional air-guiding body projects beyond the lower body of the vehicle preferably increasingly in the flow direction, in order to be able to deflect the flow to the desired extent.
In order to reduce the diagonal flow against the vehicle wheel, at least one air-guiding web or a preferably perpendicularly standing guiding fin is provided in the region of the additional air-guiding body, by which the flow on the lower side of the vehicle can be deflected to an extent that reduces the diagonal flow against it.
When the air-guiding web has a concave curvature that at least approximately corresponds to the guiding surface, the deflection of the flow is again achieved with low losses.
When the height of the air-guiding web increases at least in sections, the effect of the air-guiding web is further increased, because an endeavor, which increases in the flow direction, of flowing over the air-guiding web in the transverse direction of the vehicle, is countered at low expenditures.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.